Embodiments of the present invention relate to an interior antenna for a substrate processing chamber.
In the processing of substrates, such as semiconductor substrates and displays, a substrate is placed in a substrate processing chamber and exposed to an energized gas to deposit or etch material on the substrate. A typical process chamber comprises an enclosure wall that encloses a process zone about a substrate support, a gas supply to provide a process gas composition in the chamber, a gas energizer to energize the process gas to process the substrate, and a gas exhaust port. Such chambers can be used for chemical vapor deposition (CVD), physical vapor deposition (PVD) and etch processes.
In PVD processes, a sputtering target in the chamber faces the substrate. Process gas introduced into the chamber and ionized to form a plasma that sputters material from the target. The process gas can be energized by coupling a high frequency electric field to the gas by, for example, capacitive coupling, inductive coupling, microwave heating or combinations thereof. In a capacitively coupled plasma a voltage is applied across the target and substrate support to couple energy to the process gas. In an inductively coupled plasma (ICP) generator, a current is passed through an antenna to induce electromagnetic currents in the plasma.
An interior antenna can also be positioned inside the chamber and around the plasma generation area between the target and the substrate support. The proximity of the interior antenna to the plasma maximizes the energy being coupled to the plasma. The antenna can also be made of the same material as the target so that its surface is sputtered to provide sputtered material which deposits on the peripheral region of the substrate to equalize sputter deposition rates at the peripheral regions of the substrate to those obtained at the central substrate regions. An annular antenna can also serve to “collimate” the plasma energy to provide better filling of high aspect ratio contact holes in the substrate without forming voids in the holes from the accumulation of sputtered material at the edges of the holes.
However, the sputtered target material also deposits on the exposed surfaces of the interior annular antenna and such accumulated deposits can cause the antenna to deform and bend. Antenna deformation may also arise from thermal expansion in the elevated plasma temperatures. Such deformation can cause the antenna to electrical short when expanded portions of the antenna touch surrounding grounded conductors. Antenna deformation also makes it difficult to reinsert and bolt an antenna in the chamber after the accumulated deposited material is cleaned off the antenna. The entire antenna can also change dimensions to become asymmetrically elliptical from the originally circular geometry or have a wider spacing about its termination points, and consequently, to no longer fit the electrical connections posts used to support the antenna.
Accordingly, it is desirable to have an antenna that provides good energy transfer to a plasma in a process chamber. It is also desirable to have an antenna capable of receiving accumulated deposits without excessive deformation.